One preferred application of the present invention is in circuit interrupting or breaking devices. As used herein, the expression "circuit breaker" encompasses any device which interrupts current in an electrical circuit. This expression is not intended to be limited to devices that perform additional functions, such as, for example, reclosing. The background of the invention is described below in connection with circuit breakers generally. However, it should be noted that, except where they are expressly so limited, the claims at the end of this specification are not intended to be limited to applications of the invention in a circuit breaker.
One use of a circuit breaker is in the distribution of three phase electrical energy. When a sensor or protective relay detects a fault or other system disturbance on the protected circuit, the circuit breaker operates to physically separate current-carrying contacts in each of the three phases by opening the circuit to prevent the continued flow of current. The major components of a circuit breaker include the interrupters, which function to open and close one or more sets of current carrying contacts housed therein; the circuit switching mechanism, which provides the energy necessary to open or close the contacts; the arcing control mechanism and interrupting media, which create an open condition in the protected circuit; one or more tanks for housing the interrupters; and the bushings, which carry the high voltage electrical energy from the protected circuit into and out of the tank(s). The present invention particularly relates to the circuit switching mechanism.
An example of a circuit breaker is depicted in FIG. 1. As shown, the circuit breaker assembly 1 includes three cylindrical metal tanks 3. The three cylindrical tanks 3 form a common tank assembly 4 which is preferably filled with an inert, electrically insulating gas (e.g., SF6). The tank assembly 4 is referred to as a "dead tank" in that it is at ground potential. Each tank 3 houses an interrupter (not shown). The interrupters are provided with terminals connected to respective spaced bushing insulators. The bushing insulators are shown as bushing insulators 5a and 6a for the first phase; 5b and 6b for the second phase; and 5c and 6c for the third phase. Associated with each pole or phase is a current transformer 7. The circuit switching mechanism, or "operating mechanism," for opening and closing the interrupter contacts is contained within an operating mechanism housing 9. The operating mechanism is mechanically coupled to each of the interrupters via a linkage 8.
One example of a circuit breaker operating mechanism is disclosed in U.S. Pat. No. 4,162,385, Jul. 24, 1979, titled "Dual Spring Circuit Interrupter Apparatus." The disclosed mechanism includes an opening spring disposed within a closing spring. The mechanism is configured such that the opening spring will be charged with the charging of the closing spring. When a circuit breaker opening operation is called for, the non-fixed end of the opening spring is released, thus allowing the opening spring to discharge while the closing spring remains charged. Consequently, the closing and opening springs may be charged by simultaneously compressing the two springs.
The charging system disclosed in U.S. Pat. No. 4,162,385, for compressing the opening and closing springs, includes a relatively complex ratchet and pawl arrangement. Such a complex arrangement adds significantly to the overall cost of the circuit breaker and is thus unsuitable for use in a low cost, relatively simple circuit interrupting mechanism not requiring reclosing capability. Accordingly, a primary goal of the present invention is to provide a simple, reliable, and inexpensive charging system for a circuit switching or interrupting mechanism not requiring the complexity of a recloser.